Highly Stable Metal-Organic Frameworks and Their Applications
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Metal-organic frameworks (MOFs) are a class of newly emerged porous materials. As inorganic-organic hybrid materials, MOFs exhibit many features such as crystalline structures, high surface areas, large porosities, and facile tunability However, the lack of high stability in harsh chemical conditions of most MOFs severely hampers MOFs‟ applications. This dissertation is focusing on synthesizing highly stable MOFs, developing new synthetic strategies towards single crystalline robust MOFs and their applications of catalysis, sensing as well as methane storage. In the second section, a series of highly stable porphyrinic zirconium MOFs were synthesized. PCN-222 which exhibits one of the largest one dimensional channel and extraordinary stability in acidic condition, was studied as biomimetic catalyst. PCN-224, 221, 223 and 225 were studied as CO2 fixation catalyst, alkane oxidation catalyst, catalyst for Diels Alder reaction and pH sensor respectively. In the third section, a series of highly stable mesoporous MOFs were developed. In particular, PCN-333 exhibits the largest cage (5.5nm) among all the reported MOFs while maintaining excellent stability in aqueous environment. Therefore, PCN-333(Al) was selected for enzyme immobilization. Choosing horseradish peroxidase and cytochrome c as the guest enzymes, PCN-333(Al) shows the highest immobilization amount for both enzymes among all the reported porous supports. Meanwhile, the immobilized enzymes were proved having higher catalytic activity compared to the free enzymes. In the fourth section, a new synthetic strategy towards robust Fe-MOFs, named kinetically tuned dimensional augmentation was developed. Using preformed iron carboxylate cluster, by judiciously adjusting the amount of competing reagent, 34 Fe-MOFs containing the same inorganic building block were successfully obtained with large singles crystals. Among these MOFs, PCN-250, which can be synthesized in large scale, shows one of the highest volumetric methane uptake capacity. More importantly, PCN-250 can be stable in water for more than six months without losing the porosity, which is superior to those other MOFs reported with high methane storage capacity. With its high gas uptake, extraordinary stability, and excellent scalability, PCN-250 is a viable candidate for natural gas storage for automotive applications. In summary, a series of highly stable MOFs have been synthesized for different applications. In particular, the kinetically tuned dimensional augmentation strategy has been demonstrated as a facile method to synthesize single crystalline Fe-MOFs, which greatly facilitated the development of robust Fe-MOFs for practical applications.
Feng, Dawei (2015). Highly Stable Metal-Organic Frameworks and Their Applications. Doctoral dissertation, Texas A & M University. Available electronically from